@Helen31 You need to understand the difference between INQUIRIES and REQUESTS. The former is simply someone asking a question (usually because they want something that is outside the parameters of what you advertise). All you need to do is answer them. Just ignore ‘preapprove’ or decline’.
The latter means someone is committed to booking. You do need to ‘Accept’ or ‘Decline’. If the person has Requested to stay, but is asking for something you don’t provide, or the request is inappropriate in some other way, then ask them to WITHDRAW it, so you don’t have to decline. If they don’t, then you have to decline it.
With Inquiries, you must answer within 24 hours, and with Requests, you must take action also within 24 hours. Never let either expire without some action.
All of this, and more, is explained in the Airbnb Help pages. I suggest you spend some time there reading hosting articles.